linux-kernel - Re: [PATCH 1/6] KVM: SVM: Advance instruction pointer in dr

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Message-ID: <20110222111408.GH16508@amd.com>
Date:	Tue, 22 Feb 2011 12:14:08 +0100
From:	"Roedel, Joerg" <Joerg.Roedel@....com>
To:	Avi Kivity <avi@...hat.com>, Marcelo Tosatti <mtosatti@...hat.com>
CC:	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Zachary Amsden <zamsden@...hat.com>
Subject: Re: [PATCH 1/6] KVM: SVM: Advance instruction pointer in
 dr_intercept

On Wed, Feb 09, 2011 at 12:29:39PM -0500, Joerg Roedel wrote:
> In the dr_intercept function a new cpu-feature called
> decode-assists is implemented and used when available. This
> code-path does not advance the guest-rip causing the guest
> to dead-loop over mov-dr instructions. This is fixed by this
> patch.
> 
> Signed-off-by: Joerg Roedel <joerg.roedel@....com>
> ---
>  arch/x86/kvm/svm.c |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index 73a8f1d..bfb4948 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -2777,6 +2777,8 @@ static int dr_interception(struct vcpu_svm *svm)
>  			kvm_register_write(&svm->vcpu, reg, val);
>  	}
>  
> +	skip_emulated_instruction(&svm->vcpu);
> +
>  	return 1;
>  }

Btw. Can you meanwhile apply this patch? It fixes a bug which sends the
guest into an endless loop when decode assists is available on the host.

	Joerg

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